1. Technical Field
This invention relates to clutches used on vehicles such as motorcycles, cars, busses, trucks, and trains as well as clutches used on heavy machinery or power generating equipment. More particularly, this invention relates to a structural fiber reinforced ceramic matrix composite (FRCMC) material adapted for clutch use for the entirety of components of a clutch system or for only particular components thereof. It also relates to integrally molding fiber reinforced ceramic matrix composite clutch friction pads attached to the surfaces of metal clutch parts.
2. Background Art
A clutch is used to provide transfer of rotational energy or torque from one motor or machine to another. The clutch also provides the ability to control that transfer of energy by enabling the operator to engage and disengage the clutch, and thereby provide control over the transfer of energy between the two devices. The torque transmitted is related to the actuating force, the coefficient of friction of the engaging surfaces, and to the geometry of the clutch. In addition, the lighter the component weight of the clutch components the less energy that is required to accelerate and decelerate the vehicle. Dry clutches, i.e. clutches that do not use lubricant, but use two dry materials rubbing against each other, are extremely popular ways of controlling machinery, such as industrial equipment, motorcycles, heavy trucks and automobiles. For example, vehicles with a manual transmission typically use a single dry plate, diaphragm spring type clutch as shown in FIG. 1. The clutch assembly comprises a pressure plate 6, a flywheel 4, and a clutch disk 8. Typically, the clutch disk 8 is connected via an input shaft 12 to the transmission 14 of the vehicle, while the pressure plate 6 and flywheel 4 are connected to the motor. The clutch disk 8 is trapped between the pressure plate 6 and the flywheel 4 when the clutch is engaged, thereby transferring rotational energy from the motor to the wheels through the transmission 14. The clutch disk 8 has a splined hub 18 which allows it to slide along the splines of the transmission input shaft 12. The clutch disk 8 is held in the engaged position by spring pressure exerted by a diaphragm spring in the pressure plate 6. The clutch assembly is disengaged by a clutch release system which includes a release bearing 16, typically activated via a clutch pedal (not shown). When pressure is applied to the clutch pedal to disengage the clutch, the release bearing 16 is pushed against the fingers of a diaphragm spring release mechanism 20, which in turn releases the clutch disk 8 from engagement with the pressure plate 6 and the flywheel 4.
Typically, the flywheel 4 and pressure plate 6 are made of cast iron, and the clutch disk 8 is constructed of annular organic or semi-metallic pads 22 attached to both sides of a metal disk. These pads 22 interface with the friction surfaces 10 of the pressure plate 6 and flywheel 4. Ideally, the pads 22 are made of a high friction material that resists deterioration and wear under the fairly high temperature conditions encountered when the clutch disk is engaged with the pressure plate 6 and flywheel 4. A material with a very high coefficient of friction used in the clutch components will result in the clutch engaging or locking up rapidly as the spring force is applied; a quality that is desirable in a clutch.
Over time, with the present technology, as the clutch is used, the clutch disk pads 22 tend to wear down, and the interfacing friction surfaces 10 of the pressure plate 6 and flywheel 4 become damaged (for example, scored, gauged and worn down). A primary wear-related fault which clutch mechanisms are prone to is clutch slip. Clutch slip is a self-evident condition which occurs when the clutch disk pads 22 are badly worn so that there is insufficient pressure from the pressure plate 6 when spring pressure is applied to ensure solid engagement of the clutch mechanism. The cure for clutch slip is to renew the clutch disk 8 or the clutch pads 22, and possibly resurface the pressure plate and the flywheel friction surfaces 10. Therefore, the clutch disk 8 or the clutch friction pads 22 have to be replaced often and the flywheel 4 and pressure plate 6 have to be resurfaced or replaced periodically to ensure an adequate transfer of energy required to engage and disengage the clutch. Since most of the components of the present clutch system are made of cast iron, which is heavy, a relatively high rotational inertia exists which increases the required energy to accelerate and decelerate the engine and vehicle. Additionally, the clutch disk 8, pressure plate 6 and flywheel 4 tend to spin against one another when the clutch is engaged and disengaged, resulting in a temperature rise which contributes to wear and damage of these parts, and can also reduce the coefficient of friction, thereby decreasing the efficiency of the clutch and its ability to lock up immediately. This reduced efficiency can cause slipping, leading to even more wear damage.
To prevent the common clutch problems, car, motorcycle, truck, train, and other machinery applications could utilize a better clutch system than is provided by current technology. Ideally, this improved clutch would be constructed of material that is lighter, longer wearing, and has a higher friction coefficient and friction stability over a wide temperature range, hence providing a longer life and improved performance over the present technology.
Wherefore, it is an object of this invention to provide a lightweight clutch system for motorized vehicles, machines and the like.
It is another object of this invention to provide a clutch component material that is resistant to damage in any application involving high frictional forces and high temperatures.
It is still another object of this invention to provide clutch components for motorized vehicles, machines, and the like, which have a high coefficient of friction at any temperature and which have a friction coefficient that is stable with increasing temperature.
Other objects and benefits of this invention will become apparent from the description which follows hereinafter when read in conjunction with the drawing figures which accompany it.